The invention discloses a preparation method of lubricating oil containing graphene. The preparation method comprises the following steps: A, centrifugally separating a raw material of the graphene, taking supernatant, and drying at a low temperature to obtain graphene powder after centrifugal separation; B, vacuum-drying the above graphene powder after the centrifugal separation, thus forming a crude finished product; C, enabling the crude finished product to be mixed with an additive so as to form a mixture W, dissolving in a heated solvent, uniformly stirring, filtering while hot, and heating and drying filtrate in vacuum to obtain a finished product Q; and D, by using the above finished product Q as one of components, preparing graphene lubricating liquid, wherein the graphene lubricating liquid is prepared from the following components by weight percentage: 1%-3% of the finished product Q, 1%-3% of an assistant, and the balance of base oil. The graphene in a formula is pre-processed, and shows better stability in the formula.